CN109833693B

CN109833693B - Honeycomb filter

Info

Publication number: CN109833693B
Application number: CN201811310330.5A
Authority: CN
Inventors: 加藤靖; 近藤隆宏; 松矢淳宣
Original assignee: NGK Insulators Ltd
Current assignee: NGK Insulators Ltd
Priority date: 2017-11-24
Filing date: 2018-11-06
Publication date: 2022-07-05
Anticipated expiration: 2038-11-06
Also published as: US10814266B2; CN109833693A; US20190160413A1; DE102018219053A1; DE102018219053B4

Abstract

The invention provides a honeycomb filter which can effectively inhibit the leakage of particulate matters such as soot. The honeycomb filter is provided with: a honeycomb structure part (4) having porous partition walls (1), and a plugging part (5) for plugging any one end of cells (2), wherein a cell row in which at least inflow cells (2a) and outflow cells (2B) are alternately arranged with partition walls (1) interposed therebetween in one direction is included in a cross section of the honeycomb structure part (4) orthogonal to the direction in which the cells (2) extend, the value of the porosity of the partition walls (1) at a portion (16) partitioning the inflow cells (2a) and the outflow cells (2B) is A, the value of the porosity of the partition walls (1) at an intersection (15) between 2 inflow cells (2a) is B, and the value of A/B is 0.5 to 0.95.

Description

Honeycomb filter

Technical Field

The present invention relates to honeycomb filters. More specifically, the present invention relates to a honeycomb filter which has excellent thermal shock resistance and can effectively suppress leakage of particulate matter such as soot.

Background

Internal combustion engines are used as power sources in various industries. However, exhaust gas discharged from an internal combustion engine during combustion of fuel contains particulate matter such as Soot (Soot) and Ash (Ash). For example, the restriction on removal of particulate matter discharged from diesel engines has become severe worldwide, and a honeycomb filter having a honeycomb structure is used as a filter for removing particulate matter. Hereinafter, the particulate matter may be referred to as "PM". PM is short for "Particulate Matter".

Conventionally, as a honeycomb filter for removing PM, a honeycomb filter provided with: the honeycomb structure includes a honeycomb structure portion having porous partition walls defining a plurality of cells, and a plugging portion for plugging one end of each of the cells (see, for example, patent documents 1 to 3).

In such a honeycomb filter, the porous partition walls function as a filter for removing PM. Specifically, exhaust gas containing PM is caused to flow into the honeycomb filter from the inflow end face thereof, and after the PM is collected and filtered by the porous partition walls, the purified exhaust gas is discharged from the outflow end face of the honeycomb filter. This can remove PM in the exhaust gas.

Various studies have been made on the shape of cells partitioned by partition walls in a honeycomb filter. For example, the following honeycomb filters and the like have been proposed: in a cross section taken along a plane orthogonal to the longitudinal direction of the cell, the cross-sectional area of a predetermined cell is different from the cross-sectional area of the remaining cells (see, for example, patent documents 1 and 2). As an example, there is a honeycomb filter configured such that: the cross-sectional area of the inflow end face side-opened cells (hereinafter, sometimes referred to as "inflow cells") and the cross-sectional area of the outflow end face side-opened cells (hereinafter, sometimes referred to as "outflow cells") are different. Further, for the purpose of improving the strength of the honeycomb filter and the like, there has been proposed a honeycomb filter in which the shape of the cells in the cross section is formed into a shape having an arc shape at a portion corresponding to a corner of a polygon having a square shape or more (for example, see patent documents 1 and 3).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2005-270969

Patent document 2: international publication No. 2008/117559

Patent document 3: japanese laid-open patent application No. 2010-221159

Disclosure of Invention

In the honeycomb filter described in patent document 1, a predetermined cell cross-sectional area and a remaining cell cross-sectional area are different in a cross-section cut by a plane perpendicular to the longitudinal direction of the cell. And the honeycomb filter has a ratio of the flow path hydraulic diameter of the cell having a large cross-sectional area to the flow path hydraulic diameter of the cell having a small cross-sectional area of 1.2 or more. In the honeycomb filter, at least the cells having a large cross-sectional area have a quadrangular cross-sectional shape in which at least one portion corresponding to a corner portion is formed into an arc shape, and the ratio of the minimum thickness of the portion where the partition walls intersect with each other to the thickness of the partition walls is 0.7 or more and less than 1.3.

According to the honeycomb filter described in patent document 1, it is possible to prevent a part of the portion where the partition walls intersect from being thinned, and to maintain high strength. In many conventional honeycomb filters, partition walls are alternately arranged between an inflow cell and an outflow cell. Therefore, the honeycomb filter described in patent document 1 is configured such that: when the honeycomb filter is cracked by thermal shock, cracks are relatively easily generated in the partition walls dividing the inflow cells and the outflow cells. Therefore, the honeycomb filter described in patent document 1 has the following problems: when the honeycomb filter is cracked, PM such as soot easily leaks out.

The honeycomb filter described in patent document 2 is also configured such that: the thickness of the portions where the partition walls cross is thicker than the thickness of the partition walls that divide the compartments from each other. Therefore, similarly to the honeycomb filter described in patent document 1, there are problems as follows: when the honeycomb filter is cracked, PM such as soot easily leaks out.

In the honeycomb filter described in patent document 3, the cross-sectional shape of the outlet cells is formed in an arc shape at a portion X corresponding to a corner in a polygon having at least four sides, and therefore, the strength of the portion where the partition walls intersect is relatively increased. Therefore, although the maximum temperature during regeneration of the honeycomb filter can be reduced, when cracks occur in the honeycomb filter, cracks are relatively likely to occur in the partition walls that divide the inflow cells and the outflow cells. Therefore, there are problems as follows: when the honeycomb filter is cracked, PM such as soot easily leaks out.

The present invention has been made in view of the problems of the prior art as described above. The invention provides a honeycomb filter which has excellent thermal shock resistance and can effectively inhibit the leakage of particulate matters such as soot and the like.

According to the present invention, a honeycomb filter shown below is provided.

[1] A honeycomb filter is provided with:

a honeycomb structure portion having porous partition walls arranged to surround a plurality of cells extending from an inflow end surface to an outflow end surface and forming a flow path for a fluid; and

a hole sealing portion configured to seal one of the inflow end surface side and the outflow end surface side of the cell,

the cell having the plugging portion disposed at an end portion on the outflow end surface side and having the inflow end surface side open is defined as an inflow cell,

the cell having the plugging portion disposed at an end portion on the inflow end surface side and having an opening on the outflow end surface side is defined as an outflow cell,

a cross section of the honeycomb structure portion orthogonal to a direction in which the cells extend includes a cell row in which at least the inflow cells and the outflow cells are alternately arranged in one direction with the partition walls interposed therebetween,

setting the porosity of the partition wall at a position separating the inflow compartment and the outflow compartment to a porosity A,

a value of a porosity of the partition wall at an intersection point between 2 inflow compartments among intersection points where positions of the partition wall partitioning the compartments intersect with each other is set to a porosity B,

a value obtained by dividing the porosity A by the porosity B, that is, A/B, is 0.50 to 0.95.

[2] The honeycomb filter according to the above [1], wherein the porosity A is 15 to 70%.

[3] The honeycomb filter according to the above [1] or [2], wherein the sum of the porosity A and the porosity B is 25 to 80% on average.

[4] The honeycomb filter according to any one of [1] to [3], wherein the inflow cells in a cross section of the honeycomb structural portion orthogonal to a direction in which the cells extend have a quadrangular, hexagonal, or octagonal shape.

[5] The honeycomb filter according to [4], wherein the shape of the outlet cells in a cross section of the honeycomb structure portion orthogonal to the direction in which the cells extend is a quadrangle or a hexagon.

[6] The honeycomb filter according to any one of [1] to [5], wherein an opening area S1 of 1 inflow cell is larger than an opening area S2 of 1 outflow cell.

[7] The honeycomb filter according to any one of the above [1] to [6], wherein the thickness of the partition walls is 100 to 450 μm.

The honeycomb filter of the present invention has excellent thermal shock resistance, and can effectively suppress leakage of particulate matter such as soot. That is, in the honeycomb filter of the present invention, the porosity a of the partition walls at the positions separating the inflow cells and the outflow cells is relatively lower than the porosity B of the partition walls at the intersection between the 2 inflow cells. Therefore, when cracks occur in the honeycomb filter, cracks are likely to occur at the intersection points of the partition walls. Since cracks occurring at the intersection of the partition walls occur in the diagonal direction with respect to the intersection between the inflow cells and the outflow cells, even if such cracks occur, there is no influence on PM leakage. Therefore, according to the honeycomb filter of the present invention, leakage of particulate matter such as soot can be effectively suppressed.

Drawings

Fig. 1 is a perspective view schematically showing a first embodiment of a honeycomb filter of the present invention, viewed from an inflow end face side.

Fig. 2 is a plan view schematically showing an inflow end face of the honeycomb filter shown in fig. 1.

Fig. 3 is an enlarged plan view of a part of the inflow end face of the honeycomb filter shown in fig. 2.

Fig. 4 is a sectional view schematically showing a-a' section of fig. 2.

Fig. 5 is an enlarged plan view schematically showing a part of an inflow end face of the second embodiment of the honeycomb filter of the present invention.

Fig. 6 is an enlarged plan view schematically showing a part of an inflow end face of the third embodiment of the honeycomb filter of the present invention.

Fig. 7 is a plan view schematically showing a part of an inflow end face of the second embodiment of the honeycomb filter of the present invention.

Fig. 8 is a plan view schematically showing a part of an inflow end face of the fourth embodiment of the honeycomb filter of the present invention.

Fig. 9 is a perspective view schematically showing a fifth embodiment of the honeycomb filter of the present invention, viewed from the inflow end face side.

Fig. 10 is a plan view schematically showing an inflow end face of a sixth embodiment of the honeycomb filter of the present invention.

Description of the symbols

1. 21, 41, 61, 81: partition wall, 2, 22, 42, 62, 82: compartment, 2a, 22a, 42a, 62a, 82 a: inflow compartment, 2b, 22b, 42b, 62b, 82 b: outflow compartment, 3, 83: outer peripheral wall, 4, 24, 44, 64, 84: honeycomb structure portion, 5, 25, 45, 65, 85: blind hole portion, 11, 31, 51, 71, 91: inflow end face, 12, 92: outflow end face, 15, 35, 55, 75: inflow to intersection between compartments, 16, 36, 56, 76: the point separating the inflow compartment and the outflow compartment, 86: honeycomb unit, 87: bonding layer, 100, 200, 300, 400, 500, 600: a honeycomb filter.

Detailed Description

Hereinafter, embodiments of the present invention will be described. However, the present invention is not limited to the following embodiments. Thus, it should be understood that: the following embodiments may be modified, improved, etc. as appropriate based on the general knowledge of those skilled in the art without departing from the scope of the present invention.

(1) Honeycomb filter (first embodiment):

as shown in fig. 1 to 4, a honeycomb filter 100 according to a first embodiment of the present invention includes: a honeycomb structure portion 4 having porous partition walls 1, and plugging portions 5 disposed at either end of cells 2 formed in the honeycomb structure portion 4. Here, fig. 1 is a perspective view schematically showing the first embodiment of the honeycomb filter of the present invention, viewed from the inflow end face side. Fig. 2 is a plan view schematically showing an inflow end face of the honeycomb filter shown in fig. 1. Fig. 3 is an enlarged plan view of a part of the inflow end face of the honeycomb filter shown in fig. 2. Fig. 4 is a sectional view schematically showing a-a' section of fig. 2.

The partition walls 1 of the honeycomb structural portion 4 are arranged so as to surround the plurality of cells 2, and the plurality of cells 2 extend from the inflow end face 11 to the outflow end face 12 to form flow paths for the fluid. That is, the plurality of cells 2 are partitioned by the porous partition walls 1. The plugging portion 5 is disposed to seal one end of each of the cells 2 formed in the honeycomb structural portion 4. Therefore, one end of each of the plurality of cells 2 is sealed by the sealing portion 5 disposed in the opening on the inflow end surface 11 side or the outflow end surface 12 side. In the honeycomb filter 100 of the present embodiment, the porous partition walls 1 function as a filter material for collecting PM in the exhaust gas. Here, of the plurality of cells 2, the cell 2 having the plugging portion 5 disposed at the opening on the outlet end face 12 side and having the opening on the inlet end face 11 side is referred to as an inlet cell 2 a. Among the plurality of cells 2, the cell 2 having the plugging portion 5 disposed in the opening on the inflow end surface 11 side and having the opening on the outflow end surface 12 side is referred to as an outflow cell 2 b.

The honeycomb structure portion 4 includes, in a cross section of the honeycomb structure portion 4 perpendicular to the direction in which the cells 2 extend, at least a cell row in which inflow cells 2a and outflow cells 2b are alternately arranged in one direction with partition walls 1 interposed therebetween. The "cell rows in which the inflow cells 2a and the outflow cells 2b are alternately arranged with the partition walls 1 interposed therebetween in one direction" may have at least 1 row in the cross section of the honeycomb structural portion 4. In the honeycomb filter 100 shown in fig. 1 to 4, each cell row extending in the longitudinal direction and the transverse direction of the sheet is a cell row in which the inflow cells 2a and the outflow cells 2b are alternately arranged.

The term "cell row in which the inflow cells 2a and the outflow cells 2b are alternately arranged with the partition walls 1 interposed therebetween in one direction" refers to a cell row configured as follows when the cross-sectional shapes of the inflow cells 2a and the outflow cells 2b are polygonal. That is, the above-mentioned cell rows refer to: the cell array is formed by arranging the inflow cells 2a and the outflow cells 2b so as to be partitioned by partition walls 1 formed by 2 sides of the polygonal inflow cells 2a and the polygonal outflow cells 2b facing each other. Therefore, the "cell row in which the inflow cells 2a and the outflow cells 2b are alternately arranged with the partition walls 1 interposed therebetween in one direction" does not include a cell row in which a plurality of cells are arranged so that the vertices of the cross-sectional shapes of the cells face each other (that is, the vertices of polygonal cells face each other). The partition wall 1 present at a position where the apexes of the cross-sectional shapes of the plurality of cells face each other is the "intersection portion 15" described later.

The honeycomb filter 100 of the present embodiment is characterized in that the porosity (porosity a) of the cell walls 1 at the positions 16 partitioning the inflow cells 2a and the outflow cells 2B and the porosity (porosity B) of the cell walls 1 at the intersection points 15 between the 2 inflow cells 2a show different values. More specifically, the porosity of the partition wall 1 at the position 16 separating the inflow compartment 2a and the outflow compartment 2b is set to the porosity a. Further, of the intersection portions 15 where the portions of the partition walls 1 partitioning the cells 2 from each other (for example, the partitioning portions 16) intersect with each other, the porosity of the partition walls 1 at the intersection portions 15 where 2 cells flow into the cells 2a is set to the porosity B. In this case, "porosity a/porosity B" which is a value obtained by dividing porosity a by porosity B is 0.50 to 0.95. Hereinafter, the "porosity a/porosity B" may be simply referred to as "a/B". In the honeycomb filter 100 of the present embodiment, when cracks occur in the honeycomb filter 100 by setting the value of "a/B" to the above numerical value range, cracks are likely to occur in the intersection 15 between the inflow cells 2a on the inflow end surface 11 side. Further, cracks are likely to occur in the intersection 15 between the outlet cells 2b on the outlet end surface 12 side. That is, cracks generated in the intersection 15 are generated in the diagonal direction in the intersection 15 due to the influence of the temperature difference in the honeycomb filter 100. In particular, cracks are likely to occur in the diagonal direction connecting the cells 2 in which the plugging portions 5 are not disposed, and cracks are less likely to occur in the diagonal direction connecting the cells 2 in which the plugging portions 5 are disposed, on the inflow end surface 11 side and the outflow end surface 12 side of the honeycomb filter 100. Here, even if a crack is generated at the intersection 15 between the inlet cells 2a on the inlet end surface 11 side of the honeycomb filter 100, the influence of the leakage of PM is not exerted. Similarly, even if a crack is generated at the intersection 15 between the outlet cells 2b on the outlet end face 12 side of the honeycomb filter 100, the influence of the leakage of PM is not exerted. Therefore, according to the honeycomb filter 100 of the present embodiment, leakage of PM such as soot can be effectively suppressed.

In the present specification, the "intersection portion 15" refers to a portion where portions of the partition wall 1 that separate the compartments 2 from each other intersect with each other. Specifically, the cross section of the honeycomb structure portion 4 perpendicular to the direction in which the cells 2 extend is defined as follows. The "intersection portion 15" means: in the partition walls 1 arranged in a lattice shape so as to surround the plurality of cells 2, a portion where the partition walls 1 arranged in a first direction constituting the lattice and the partition walls 1 arranged in a second direction different from the first direction intersect with each other (a portion where lattice lines overlap). Here, the "first direction of the lattice" includes a direction parallel to a portion of the partition wall 1 partitioning the 2 cells 2, and a locus like a single stroke is drawn along the partition wall 1. In addition, when the partition walls 21 are bent in the first direction of the lattice with respect to the first direction as in the honeycomb filter 200 shown in fig. 5 described later, a direction in which the bending angle of the partition walls 21 with respect to the first direction becomes smaller is selected. The "second direction of the lattice" may be defined in the same manner as the "first direction of the lattice" described above.

Hereinafter, in the honeycomb filter 100 shown in fig. 1 to 4, the value of the porosity of the partition walls 1 at the portion 16 separating the inflow cells 2a and the outflow cells 2b may be simply referred to as "porosity a" in the present specification. The portion 16 that partitions the inflow compartment 2a and the outflow compartment 2b includes, for example, a portion 16 that partitions the inflow compartment 2a and the outflow compartment 2b in a compartment row in which the inflow compartment 2a and the outflow compartment 2b are alternately arranged with the partition wall 1 interposed therebetween in one direction. The value of the porosity of the partition wall 1 at the intersection 15 between the 2 inflow compartments 2a may be simply referred to as "porosity B". For example, when the shape of the cell 2 is a quadrangle, "the intersection 15 between the 2 inflow cells 2 a" is a "portion where the vertexes of the cross-sectional shapes of the 2 or more inflow cells 2a face each other". Therefore, 3 or more than 3 inflow compartments 2a may be arranged to face each other at "the intersection 15 between 2 inflow compartments 2 a". The "apex of the cross-sectional shape of the inflow compartment 2 a" may be rounded or chamfered linearly at a position corresponding to the apex of the cross-sectional shape. In addition, when the quadrangular cells 22 and the octagonal cells 22 are alternately arranged in a single cell row with the partition walls 21 interposed therebetween, as in the honeycomb filter 200 shown in fig. 5 described later, the octagonal cells 22 can be regarded as the chamfered quadrangular cells 22.

In the present invention, the porosity a and the porosity B of the partition wall 1 are values obtained by the following methods. First, a sample piece for measuring the porosity a and the porosity B is cut out from the honeycomb filter 100. The cut portion of each sample piece was 5 on the inflow end face 11 side and the outflow end face 12 side of the honeycomb filter 100, and the total was 10. The cut-out portion in each end face was defined as the 1 st cut-out portion at the center position of each end face. In each end face, 4 points on the X axis and the Y axis passing through the center position and orthogonal to each other, which are intermediate points between the center position and the outer peripheral edge of the honeycomb filter 100, are set as remaining 4 cut-out portions.

The sample sheet for determining porosity a was cut into: the partition walls 1 respectively including the central portions of the partition walls 1 partitioning the inflow compartment 2a and the outflow compartment 2b are provided at 10 described above. The sample piece for measuring the porosity a had one length of the thickness of the partition wall 1 in the central portion, the other length of 100 μm in the direction in which the partition wall 1 in each end face extends, and the other length of 20mm in the direction in which the cell 2 extends.

The sample sheet for determining porosity B was cut into: at 10, the center portions of the intersection portions 15 of the partition walls 1 are included. The sample piece for measuring the porosity B was formed such that a square with a side length of 100 μm with the center of the intersection 15 of the partition wall 1 as the center was an end face and the length in the axial direction was 20mm along the direction in which the cell 2 extended.

The sample piece cut out from the honeycomb filter 100 in this manner is embedded in an epoxy resin and fixed, and then the surface thereof is polished. Then, each sample piece was cut out by 5mm in the entire length direction, and the cut surface was an observation surface of a scanning electron microscope (hereinafter, also referred to as "SEM"). SEM is short for "Scanning Electron Microscope". As the scanning electron microscope, for example, a model of "scanning electron microscope" manufactured by hitachi high and new technology corporation: S3200-N ".

Then, the observation surface of the prepared sample piece was observed by SEM to obtain an SEM image. In the measurement of the porosity a of the partition wall 1, the SEM image was obtained for the partition wall 1 in each observation plane of the 10 sample pieces. The SEM image was magnified to 100 times for observation. In addition, when the porosity B of the partition wall 1 is measured, the SEM image is acquired at the intersection 15 of the partition wall 1 in each observation plane of the 10 sample pieces. Next, using image analysis software, "the area of the partition wall 1S 1" and "the area of the pore portion (void portion) S2" were calculated for each image. Then, using "calculation formula (1): S2/(S1+ S2) ", the porosity of the partition wall 1 captured in each image is calculated. The average value of the porosity at 10 points was used for the values of S1 and S2.

In the honeycomb filter 100 for measuring the porosity, when a catalyst (not shown) for purifying exhaust gas is supported on the surfaces of the cell walls 1 and inside the pores of the cell walls 1, the porosity is determined by considering the portions on which the catalyst is supported as the pore portions of the cell walls 1. That is, in the above-described method for measuring the porosity a and the porosity B, after taking an SEM image, the area determined to have the catalyst on the basis of the color information in the obtained SEM image is recognized as the pore portion of the partition wall 1, and the porosity is determined.

If the value obtained by dividing the porosity a by the porosity B, that is, a/B, is less than 0.50, cracks may be continuously generated in 2 or more of the intersection points 15 arranged adjacent to each other on the diagonal line among the intersection points 15 of the partition walls 1, and it may be difficult to sufficiently suppress PM leakage. Further, if the a/B exceeds 0.95, cracks are likely to occur in the partition wall 1 at the portion 16 that separates the inflow compartment 2a and the outflow compartment 2B, and it is difficult to suppress leakage of PM.

A value obtained by dividing the porosity A by the porosity B, that is, A/B, is 0.50 to 0.95, preferably 0.55 to 0.90. With such a configuration, leakage of PM such as soot can be more effectively suppressed.

The value of the porosity B is not particularly limited, but is preferably 25 to 80%, more preferably 30 to 75%. If the value of the porosity B is less than 25%, the pressure loss may increase. If the value of the porosity B exceeds 80%, the Isostatic strength (Isostatic strength) of the honeycomb filter 100 may decrease. The value of the porosity a is also not particularly limited, and is preferably 15 to 70%, for example.

The sum of the porosity A and the porosity B is preferably 20 to 75% on average, more preferably 25 to 70% on average. If the sum of the porosity a and the porosity B is less than 20% on average, the pressure loss may increase. Further, if the sum average of the porosity a and the porosity B exceeds 75%, the isostatic strength of the honeycomb filter 100 may decrease.

The shape of each cell 2 (hereinafter, also simply referred to as "cell shape") in a cross section of the honeycomb structure portion 4 orthogonal to the direction in which the cells 2 extend is not particularly limited. For example, the shape of the inflow compartment 2a is preferably quadrangular, hexagonal or octagonal. In addition, the outflow compartment 2b is preferably quadrangular or hexagonal in shape. The shape of each cell 2 may be a shape in which corners of a polygon are formed in a curved shape, for example, a substantially quadrangular shape in which corners of a quadrangular shape are formed in a curved shape.

The thickness of the partition wall 1 is preferably 100 to 450 μm, more preferably 120 to 430 μm, and particularly preferably 140 to 400 μm. If the thickness of the partition walls 1 is less than 100 μm, the isostatic strength of the honeycomb filter 100 may be reduced. If the thickness of the partition wall 1 exceeds 450 μm, the pressure loss may increase, resulting in a decrease in the output of the engine or a deterioration in fuel consumption. The thickness of the partition wall 1 is a value measured by a method of observing a cross section perpendicular to the axial direction of the honeycomb filter 100 with an optical microscope.

The overall shape of the honeycomb filter 100 is not particularly limited. For example, the honeycomb filter 100 shown in fig. 1 to 4 has an overall cylindrical shape in which the inflow end face 11 and the outflow end face 12 are circular. For example, the honeycomb filter 100 may have a substantially circular columnar shape such as an oval shape, a Racetrack (Racetrack) shape, or an oblong shape in the inflow end surface and the outflow end surface. The honeycomb filter 100 may have an overall shape in which the inlet end surface 11 and the outlet end surface 12 are polygonal prisms such as a quadrangle or a hexagon.

The material constituting the partition wall 1 is not particularly limited, and from the viewpoint of strength, heat resistance, durability, and the like, various ceramics, metals, and the like, which are oxides or non-oxides, are preferable as the main component. Specifically, for example, cordierite, Mullite (Mullite), alumina, Spinel (Spinel), silicon carbide, silicon nitride, aluminum titanate, and the like are considered as ceramics. As the metal, Fe-Cr-Al based metal, metallic silicon, and the like are considered. Preferably, 1 or 2 or more selected from these materials are used as the main component. From the viewpoint of high strength, high heat resistance, and the like, it is particularly preferable to use 1 or 2 or more species selected from the group consisting of alumina, mullite, aluminum titanate, cordierite, silicon carbide, and silicon nitride as the main component. Silicon carbide or a silicon-silicon carbide composite material is particularly suitable from the viewpoint of high thermal conductivity, high heat resistance, and the like. Here, "main component" means a component constituting 50 mass% or more of the partition wall 1. The material constituting the partition wall 1 preferably contains the above-described component in an amount of 70 mass% or more, and more preferably contains the above-described component in an amount of 80 mass% or more.

The material of the plugging portion 5 is preferably a material preferable as the material of the partition wall. The material of the plugging portion 5 and the material of the partition wall 1 may be the same material or different materials.

In the honeycomb filter 100 of the present embodiment, the exhaust gas-purifying catalyst may be supported on at least one of the surfaces of the partition walls 1 and the pores of the partition walls 1 of the honeycomb structural portion 4. With such a configuration, CO, NOx, HC, and the like in the exhaust gas can be made harmless by the catalytic reaction. Further, oxidation of soot trapped in the partition walls 1 can be promoted.

When a catalyst is supported on the honeycomb filter 100 of the present embodiment, the catalyst preferably includes 1 or more selected from the group consisting of an SCR catalyst, an NOx storage catalyst, and an oxidation catalyst. The SCR catalyst is a catalyst that selectively reduces a component to be purified. In particular, the SCR catalyst is preferably an SCR catalyst for selective NOx reduction that selectively reduces NOx in the exhaust gas. In addition, as the SCR catalyst, zeolite substituted with metal can be mentioned. Examples of the metal for substituting the zeolite include iron (Fe) and copper (Cu). As the zeolite, beta zeolite is cited as a preferable example. The SCR catalyst may be a catalyst containing at least 1 selected from the group consisting of vanadium and titanium dioxide as a main component. Examples of the NOx storage catalyst include alkali metals and alkaline earth metals. Examples of the alkali metal include potassium, sodium, and lithium. Examples of the alkaline earth metal include calcium. Examples of the oxidation catalyst include an oxidation catalyst containing a noble metal. Specifically, the oxidation catalyst preferably contains at least one selected from the group consisting of platinum, palladium, and rhodium.

(2) Honeycomb filter (second to sixth embodiments):

next, second to sixth embodiments of the honeycomb filter of the present invention will be described with reference to fig. 5 to 10. Here, fig. 5 is an enlarged plan view schematically showing a part of the inflow end face of the second embodiment of the honeycomb filter of the present invention. Fig. 6 is an enlarged plan view schematically showing a part of an inflow end face of the third embodiment of the honeycomb filter of the present invention. Fig. 7 is a plan view schematically showing a part of an inflow end face of the second embodiment of the honeycomb filter of the present invention. Fig. 8 is a plan view schematically showing a part of an inflow end face of the fourth embodiment of the honeycomb filter of the present invention. Fig. 9 is a perspective view schematically showing a fifth embodiment of the honeycomb filter of the present invention, viewed from the inflow end face side. Fig. 10 is a plan view schematically showing an inflow end face of a sixth embodiment of the honeycomb filter of the present invention.

As shown in fig. 5 and 7, a honeycomb filter 200 according to a second embodiment of the present invention includes: a honeycomb structure portion 24 having porous partition walls 21, and a plugging portion 25 disposed at one end of each of the cells 22 formed in the honeycomb structure portion 24. The honeycomb structure portion 24 includes at least a cell row in which inflow cells 22a and outflow cells 22b are alternately arranged in one direction with partition walls 21 interposed therebetween, in a cross section of the honeycomb structure portion 24 orthogonal to the direction in which the cells 22 extend.

With the honeycomb filter 200 of the second embodiment, the inflow cells 22a are "octagonal" in shape, and the outflow cells 22b are "quadrangular" in shape. The octagonal inflow compartment 22a has a relatively larger cross-sectional area than the quadrangular outflow compartment 22 b. When the porosity of the partition wall 21 at the position 36 that separates the inflow compartment 22a from the outflow compartment 22B is A and the porosity of the partition wall 21 at the intersection 35 between 2 inflow compartments 22a is B, the A/B ratio is 0.5 to 0.95. The honeycomb filter 200 of the second embodiment configured as described above can also obtain the same operational advantages as the honeycomb filter 100 of the first embodiment (see fig. 1 to 4) described above. The honeycomb filter 200 of the second embodiment is preferably configured in the same manner as the honeycomb filter 100 of the first embodiment (see fig. 1 to 4), except that the shapes of the inflow cells 22a and the outflow cells 22b are different. In addition, in the case where the quadrangular cells 22 and the octagonal cells 22 are alternately arranged in a single cell row with the partition walls 21 interposed therebetween, the octagonal cells 22 can also be regarded as chamfered quadrangular cells 22.

In the honeycomb filter 200, the cross-sectional area of the inflow cells 22a is relatively larger than the cross-sectional area of the outflow cells 22b, and therefore, even if cracks occur in the honeycomb filter 200, leakage of PM such as soot can be more effectively suppressed. That is, in a situation where cracks occur in the honeycomb filter 200, the "intersection 35" which is a portion that partitions the inflow cells 22a from each other and is less likely to affect the PM leakage may be more preferentially cracked. Therefore, the "portion 36 separating the inflow compartment 22a and the outflow compartment 22 b" can be made less likely to cause a crack that connects the inflow compartment 22a and the outflow compartment 22 b.

In the case where the opening area S1 of 1 inflow cell 22a is larger than the opening area S2 of 1 outflow cell 22b like the honeycomb filter 200, the ratio (S2/S1) of the opening area S2 to the opening area S1 is preferably 0.20 to 0.95, more preferably 0.30 to 0.90. With such a configuration, it is possible to very effectively suppress the occurrence of cracks connecting the inflow cell 22a and the outflow cell 22b at the intersection 35.

As shown in fig. 6, a honeycomb filter 300 according to a third embodiment of the present invention includes: a honeycomb structure 44 having porous partition walls 41, and a plugging portion 45 disposed at one end of each of the cells 42 formed in the honeycomb structure 44. The honeycomb structure portion 44 includes at least a cell row in which inflow cells 42a and outflow cells 42b are alternately arranged in one direction with partition walls 41 interposed therebetween in a cross section of the honeycomb structure portion 44 perpendicular to the direction in which the cells 42 extend.

In the honeycomb filter 300 of the third embodiment, the inflow cells 42a are shaped like "quadrangles with rounded vertices", and the outflow cells 42b are shaped like "quadrangles". The inflow compartment 42a has a relatively larger cross-sectional area than the outflow compartment 42 b. When the porosity of the partition wall 41 at the position 56 that separates the inflow compartment 42a and the outflow compartment 42B is defined as A and the porosity of the partition wall 41 at the intersection 55 between the 2 inflow compartments 42a is defined as B, the A/B ratio is 0.5 to 0.95. The honeycomb filter 300 of the third embodiment configured as described above can also obtain the same operational advantages as the honeycomb filter 100 (see fig. 1 to 4) of the first embodiment described above. The honeycomb filter 300 of the third embodiment is preferably configured in the same manner as the honeycomb filter 100 of the first embodiment (see fig. 1 to 4), except that the shapes of the inflow cells 42a and the outflow cells 42b are different.

As shown in fig. 8, a honeycomb filter 400 according to a fourth embodiment of the present invention includes: a honeycomb structure portion 64 having porous partition walls 61, and a sealing portion 65 disposed at one end of each of the cells 62 formed in the honeycomb structure portion 64. The honeycomb structure 64 includes at least a cell row in which inflow cells 62a and outflow cells 62b are alternately arranged in one direction with partition walls 61 interposed therebetween in a cross section of the honeycomb structure 64 perpendicular to the direction in which the cells 62 extend.

In the honeycomb filter 400 of the fourth embodiment, each of the inflow cells 62a and the outflow cells 62b has a "hexagonal" shape. When the porosity of the partition wall 61 at a portion 76 that separates the inflow compartment 62a and the outflow compartment 62B is defined as A and the porosity of the partition wall 61 at an intersection 75 between 2 inflow compartments 62a is defined as B, the A/B ratio is 0.5 to 0.95. The honeycomb filter 400 of the fourth embodiment configured as described above can also obtain the same operational advantages as the honeycomb filter 100 of the first embodiment (see fig. 1 to 4) described above. The honeycomb filter 400 of the fourth embodiment is preferably configured in the same manner as the honeycomb filter 100 of the first embodiment (see fig. 1 to 4), except that the shapes of the inflow cells 62a and the outflow cells 62b are different.

When the cells 62 have a hexagonal shape, there are 2 kinds of intersection points 75, that is, "intersection points 75 existing between 2

inflow cells

62a and 1 outflow cell 62 b" and "intersection points 75 existing between 3 inflow cells 62 a" as "intersection points 75 among 2 inflow cells 62 a". In the honeycomb filter 400 of the present embodiment, when the porosity at one of the intersection portions 75 of the 2 types of intersection portions 75 is set to the porosity B, a/B may be set to 0.50 to 0.95. When the porosity at the intersection 75 between the 3 inflow cells 62a is set to the porosity B, a/B is more preferably 0.50 to 0.95.

As shown in fig. 9, a fifth embodiment of the honeycomb filter of the present invention is a honeycomb filter 500 including: a honeycomb structure portion 84, and a plugging portion 85 disposed at one end of each of the cells 82 formed in the honeycomb structure portion 84. In particular, in the honeycomb filter 500, each honeycomb structure portion 84 is formed of the columnar honeycomb cells 86, and the side surfaces of the plurality of honeycomb cells 86 are joined by the joining layer 87. That is, in the honeycomb filter 500 of the present embodiment, each honeycomb cell 86 constituting the honeycomb filter having a cell structure is the honeycomb structure portion 84 in the honeycomb filter 500. Here, the "honeycomb filter having a cell structure" is a honeycomb filter formed by joining a plurality of honeycomb cells 86 that are separately produced. The honeycomb filter 100 shown in fig. 1 to 4 in which all the partition walls 1 of the honeycomb structural portion 4 are integrally formed may be referred to as an "integral honeycomb filter". The honeycomb filter of the present invention may be a "honeycomb filter having a cell structure" or an "integrated honeycomb filter".

In the honeycomb filter 500, at least 1 honeycomb cell 86 is preferably configured in the same manner as the honeycomb structure portion of the honeycomb filter of the first embodiment described above. The honeycomb filter 500 as described above can also provide the same operational advantages as those of the honeycomb filter of the first embodiment described above. The plurality of honeycomb units 86 may have the same cell structure or different cell structures.

The outer peripheral wall 83 in the honeycomb filter 500 is preferably an outer peripheral coating layer formed of an outer peripheral coating material. The outer periphery coating material is a coating material for forming an outer periphery coating by being applied to the outer periphery of a joined body obtained by joining the plurality of honeycomb cells 86. In addition, in the joined body obtained by joining the plurality of honeycomb cells 86, it is preferable that the outer peripheral coating layer described above is provided by grinding the outer peripheral portion of the joined body. In the integrated honeycomb filter 100 shown in fig. 1 to 4, the outer peripheral wall 3 disposed on the outer periphery of the honeycomb structural portion 4 may be an outer peripheral coating layer formed of the outer peripheral coating material as described above.

In the honeycomb filter 500 shown in fig. 9, the cells 82 (i.e., the inflow cells 82a and the outflow cells 82b) have a quadrangular shape. However, the shape of each cell 82 in each honeycomb unit 86 is not limited to a quadrangle, and the shape of the cell in the honeycomb filter of the first to fourth embodiments described above may be adopted.

As shown in fig. 10, a sixth embodiment of the honeycomb filter of the present invention is a honeycomb filter 600 including: a honeycomb structure portion 4, and a plugging portion 5 disposed at one end of each of the cells 2 formed in the honeycomb structure portion 4. In particular, in the honeycomb filter 600, the honeycomb filter 600 has a columnar shape with an elliptical end face as a whole. That is, as shown in fig. 10, the inflow end surface 11 has an elliptical shape. It is preferably configured in the same manner as the honeycomb filter 100 (see fig. 1 to 4) of the first embodiment, except that the honeycomb filter 600 has a different overall shape.

In the honeycomb filter 600 shown in fig. 10, the cells 2 (i.e., the inflow cells 2a and the outflow cells 2b) have a quadrangular shape. However, the shape of the cells 2 is not limited to the quadrangle, and the shapes of the cells in the honeycomb filters of the first to fourth embodiments described above may be adopted.

(3) The manufacturing method of the honeycomb filter comprises the following steps:

next, a method for manufacturing the honeycomb filter of the present invention will be explained. As a method for producing a honeycomb filter of the present invention, there is a method comprising: a step of producing a honeycomb formed body, a step of forming a plugging portion at an opening of a cell, and a step of drying and firing the honeycomb formed body.

(3-1) Molding Process:

the molding step is a step of extruding the kneaded material into a honeycomb shape to obtain a honeycomb molded body. The honeycomb formed body has: the partition wall defines a compartment extending from the first end surface to the second end surface, and an outer peripheral wall formed to surround an outermost periphery of the compartment wall. The honeycomb structure portion is a portion of the honeycomb structure formed by the partition walls. In the molding step, first, the molding material is kneaded to prepare a clay. Next, the obtained clay was extruded to obtain a honeycomb formed body in which the partition walls and the outer peripheral wall were integrally formed.

The molding material is preferably obtained by adding a dispersion medium and additives to a ceramic material. Examples of the additive include an organic binder, a pore-forming material, and a surfactant. Examples of the dispersion medium include water. As the molding material, the same molding material as used in a conventionally known method for manufacturing a honeycomb filter can be used.

Examples of the method of kneading the molding material to form the clay include a method using a kneader, a vacuum pug mill, or the like.

The extrusion molding can be performed using a die for extrusion molding in which a slit corresponding to the cross-sectional shape of the honeycomb molded body is formed. For example, as the die for extrusion molding, a die in which slits corresponding to the shapes of the cells in the honeycomb filters of the first to fourth embodiments described above are formed is preferably used.

Here, in the extrusion molding, it is preferable to increase the extrusion pressure by increasing the extrusion speed at the time of molding. By performing extrusion molding in such a manner, "the partition wall at the portion separating the inflow compartment and the outflow compartment" can be made denser than other portions. That is, in the obtained honeycomb filter, the "porosity B of the partition walls at the intersection between the 2 inflow cells" can be relatively increased. Thus, A/B can be adjusted to a numerical range of 0.5 to 0.95, wherein A/B is a value obtained by dividing the porosity A of the partition wall at the position where the inflow compartment and the outflow compartment are separated by the porosity B of the partition wall at the intersection between 2 inflow compartments.

(3-2) sealing step:

the sealing step is a step of forming a sealing portion by sealing the openings of the cells. For example, in the sealing step, the openings of the cells are sealed with the same material as that used for producing the honeycomb formed body, thereby forming the sealing portions. The method for forming the plugged portion may be performed according to a conventionally known method for manufacturing a honeycomb filter.

(3-3) firing step:

the firing step is a step of firing the honeycomb molding formed with the plugging portion to obtain a honeycomb filter. Before the honeycomb formed body having the plugging portion formed therein is fired, the obtained honeycomb formed body may be dried by, for example, microwaves and hot air. For example, the honeycomb formed body before the formation of the plugging portions may be subjected to the firing step, and then the honeycomb fired body obtained by the firing step may be subjected to the plugging step described above.

The firing temperature at the time of firing the honeycomb formed article may be appropriately determined depending on the material of the honeycomb formed article. For example, when the material of the honeycomb formed body is cordierite, the firing temperature is preferably 1380 to 1450 ℃, more preferably 1400 to 1440 ℃. The firing time is preferably about 4 to 6 hours in terms of the holding time at the maximum temperature.

Examples

The present invention will be described more specifically with reference to the following examples, but the present invention is not limited to these examples at all.

(example 1)

To 100 parts by mass of a cordierite raw material, 0.5 part by mass of a pore-forming material, 33 parts by mass of a dispersion medium, and 5.6 parts by mass of an organic binder were added, and the mixture was mixed and kneaded to prepare a clay. As the cordierite forming raw material, alumina, aluminum hydroxide, kaolin, talc, and silica are used. Water is used as a dispersion medium, a water-absorbent polymer having an average particle diameter of 10 to 50 μm is used as a pore-forming material, Methylcellulose (Methylellulose) is used as an organic binder, and Dextrin (Dextrin) is used as a dispersant.

Next, the kneaded material was extruded using a predetermined die to obtain a honeycomb formed body having a rectangular cell shape and a cylindrical overall shape. In the extrusion molding, a die for extrusion molding in which slits corresponding to the cross-sectional shape of the honeycomb formed body are formed is used, and in the extrusion molding, the extrusion speed is increased and the extrusion pressure is increased as compared with the extrusion molding in comparative example 1 described later, so that the molding is performed.

Next, the honeycomb formed body was dried by a hot air dryer. The temperature of the atmosphere during drying is 95-145 ℃.

Next, plugging portions are formed in the dried honeycomb formed body. Specifically, first, a mask is applied to the inflow end face of the honeycomb formed body so that the inflow cells are covered. Then, the end portion of the honeycomb formed body to which the mask is applied is immersed in the sealing slurry, and the opening portions of the outflow cells to which no mask is applied are filled with the sealing slurry. Then, the sealing slurry is also filled into the openings of the inflow cells in the outflow end face of the honeycomb formed body in the same manner as in the above-described method. Then, the honeycomb formed body having the plugging portion formed thereon is further dried by a hot air dryer.

Next, the dried honeycomb formed body is fired to produce a honeycomb fired body. The firing atmosphere temperature is 1350-1440 ℃, and the firing time is 10 hours.

Next, the wall material disposed at the outer peripheral portion of the honeycomb fired body was removed by grinding, and an outer peripheral coating material was applied to the outer peripheral portion to produce an outer peripheral wall made of the outer peripheral coating material. A ceramic slurry prepared by mixing cordierite particles having an average particle diameter of 20 to 50 [ mu ] m and a particle diameter of 90% or less of 150 [ mu ] m as ceramic particles with colloidal silica, alumina fibers and water is used as an outer periphery coating material. The honeycomb filter in which the outer peripheral wall of the honeycomb filter is formed using the outer peripheral coating material as described above is referred to as "outer peripheral machining" in the column of "method of forming outer peripheral wall" in table 1. On the other hand, a honeycomb filter in which the outer peripheral portion of the honeycomb formed body obtained by extrusion molding was directly used as the outer peripheral wall was described as "integrated" in the column of "method for forming outer peripheral wall" in table 1.

For the honeycomb filter of example 1, the thickness of the partition walls was 300 μm, and the cell density was 46.5 cells/cm². The cell shape in a cross section of the honeycomb filter orthogonal to the direction in which the cells extend is a quadrangle. The column "cell structure" in table 1 shows the thickness of the partition wall, cell density, and cell shape.

The honeycomb filter of example 1 has a circular cross section orthogonal to the axial direction, and the honeycomb structure portion has a cell row in which inflow cells 2a and outflow cells 2b are alternately arranged with partition walls 1 interposed therebetween, as shown in fig. 3. The shape of the honeycomb filter of example 1 is shown in columns "sectional shape", "diameter", and "overall length" of table 1.

The honeycomb filter of example 1 was measured for "porosity a of partition walls at a position separating inflow cells and outflow cells" and "porosity B of partition walls at a crossing point between 2 inflow cells" by the following method. Further, the average porosity and the porosity ratio were determined from the values of the porosity a and the porosity B. The average porosity is the added average value of the porosity A and the porosity B (i.e., (A + B)/2). The porosity ratio is a value of porosity a to porosity B (i.e., a/B). The respective results are shown in table 2.

[ method for measuring porosity ]

First, a sample piece for measuring the porosity a and the porosity B was cut out from the honeycomb filter. The cut portions of the sample piece were 5 on the inflow end face side and the outflow end face side of the honeycomb filter, respectively, and the total number was 10. The cut-out portion in each end face is a center position (1 st position) of each end face and 4 points (2 nd to 5 th positions) which are intermediate points between the center position and the outer peripheral edge of the honeycomb filter on the X axis and the Y axis passing through the center position and orthogonal to each other. At point 10 above, sample pieces for measuring the porosity a were cut out so as to include the center portion of the partition wall separating the inflow compartment and the outflow compartment. The sample piece for measuring the porosity a had one length of the thickness of the partition wall in the central portion, the other length of the thickness of the partition wall in each end face in the direction in which the partition wall extends, and the other length of the thickness of the partition wall in the cell in the direction in which the partition wall extends, which was 20 mm. At 10 above, a sample piece for measuring the porosity B was cut out so as to include the center of the intersection of the partition walls. The sample piece for measuring the porosity B was formed such that a square with a side length of 100 μm centered on the center of the intersection of the partition walls was an end face and the length in the axial direction was 20mm in the direction in which the cells extended. Next, the prepared sample piece was embedded in an epoxy resin and fixed, and then the surface thereof was polished. Then, each sample piece was cut out by 5mm in the entire length direction, and the cut surface was observed by SEM to obtain an SEM image. The scanning electron microscope used was a model number "manufactured by hitachi high and new technology corporation: S3200-N ". In the measurement of the porosity a, SEM images magnified 100 times were obtained for the central portions of the partition walls in the observation surfaces of the 10 sample pieces. In the measurement of the porosity B, SEM images with an enlargement of 100 times were obtained for the intersection points of the partition walls in each observation surface of the above-described 10 sample pieces. Then, using image analysis software, for each image, "the partition wall area S1" and "the pore portion (void portion) area S2" were calculated, using "expression (1): S2/(S1+ S2) ", the porosity of the cell wall captured in each image is calculated. The average value of the porosity at each 10 point was used for the values of S1 and S2.

TABLE 1

TABLE 2

(examples 2 to 30)

The cell structures, the sectional shapes, the methods of forming the outer peripheral walls, and the porosities a and B of the cell walls were changed as shown in tables 1 and 2, and the honeycomb filters of examples 2 to 30 were produced. For the

Examples 3, 4, 7, 8, 15 to 18, 23, 24, 29, and 30 show the shape of the cells as shown in FIG. 5. That is, in the above embodiment, the inflow compartment is formed in an octagonal shape, and the outflow compartment is formed in a quadrangular shape. In examples 7 and 8, the cross-sectional shape of the honeycomb filter was set to an elliptical shape as shown in fig. 10. In addition, in examples 13, 14, 17, and 18, the outer peripheral portion of the honeycomb formed body obtained by extrusion molding was used as the outer peripheral wall, and the formation of the outer peripheral wall with the outer peripheral coating material was not performed.

In examples 27 to 30, silicon carbide (SiC) was used as a material for producing the honeycomb filter. The honeycomb filters of examples 27 to 30 were honeycomb filters having a cell structure.

In the production of the honeycomb filters of examples 2 to 30, the extrusion pressure during extrusion molding was adjusted, and the values of the porosity a and the porosity B of the cell walls were adjusted.

With respect to the honeycomb filters of examples 1 to 30, evaluation on "thermal shock resistance (Robustness: Robustness)" was carried out by the following method. The results are shown in Table 3.

[ thermal shock resistance (robustness) ]

As the evaluation of the thermal shock resistance, the honeycomb filter was subjected to the following test, and the robustness of the honeycomb filter was evaluated based on the presence or absence of cracks in the honeycomb filter after the test. Specifically, first, 2 to 12g/L of soot was accumulated in the honeycomb filters of the examples and comparative examples. Soot deposition was performed using an engine mount on which a 2.2L diesel engine was mounted. The engine rotational speed was set to 2000rpm and the engine torque was set to 60Nm for the operating conditions of the engine mount. Then, a regeneration process is performed by post injection to raise the inlet gas temperature of the honeycomb filter, and when the pressure loss before and after the honeycomb filter starts to decrease, the post injection is cut off, and the engine is switched to an idling state. The amount of soot deposited at this time was determined under the conditions that the maximum temperature at the center of the outflow end face was 1000 ℃ at each position in the examples and the amount of soot deposited was the same for the examples and comparative examples under the same number. Then, the honeycomb filter was visually observed for the presence or absence of cracks in the "partition walls at the positions separating the inflow cells and the outflow cells" and the "intersection points". In the above test, the presence or absence of cracks was confirmed at all the portions of the outlet end face having the highest temperature. Then, the thermal shock resistance was evaluated based on the following evaluation criteria. The results are shown in Table 3.

Evaluation A: no cracks were confirmed.

Evaluation B: there were 1 crack.

Evaluation C: the cracks have more than 2 parts and are continuous.

In the evaluation of the thermal shock resistance, the following method was used to perform the overall judgment based on the evaluation results of the above 2 points. The results are shown in Table 3. In the overall judgment, the evaluation a is passed, and the evaluations B and C are failed.

Evaluation A: no soot leaks, and the crack is 1 or less.

Evaluation B: there was no soot leakage, but the cracks were 2 or more and continuous.

Evaluation C: there is leakage of soot.

TABLE 3

Comparative examples 1 to 30

The cell structures, the sectional shapes, the methods of forming the outer peripheral walls, and the porosities a and B of the cell walls were changed as shown in tables 4 and 5, and the honeycomb filters of comparative examples 1 to 30 were produced. The honeycomb filters of comparative examples 1 to 30 were also evaluated for "thermal shock resistance (robustness)" in the same manner as in example 1. The results are shown in Table 6.

In comparative examples 3, 4, 7, 8, 15 to 18, 23, 24, 29 and 30, the shape of the cells was as shown in FIG. 5. In comparative examples 7 and 8, the cross-sectional shape of the honeycomb filter was set to an elliptical shape as shown in fig. 10. In comparative examples 13, 14, 17, and 18, the outer peripheral portion of the honeycomb formed body obtained by extrusion molding was used as the outer peripheral wall, and the outer peripheral wall was not formed with the outer peripheral coating material. In comparative examples 27 to 30, silicon carbide (SiC) was used as a material for producing the honeycomb filter. The honeycomb filters of comparative examples 27 to 30 were honeycomb filters having a cell structure. The honeycomb filters of comparative examples 1 to 30 were the same as those of examples 1 to 30, which were numbered correspondingly, except that the values of the porosity a and the porosity B were different.

TABLE 4

TABLE 5

TABLE 6

(results)

The honeycomb filters of examples 1 to 30 were able to obtain the result of "evaluation a" satisfying the pass standard in the comprehensive determination of the thermal shock resistance. In particular, in the honeycomb filters of examples 1 to 30, no cracks were observed at all in the "portions separating the inflow cells and the outflow cells (in other words, the substantial wall portions of the partition walls)". Note that, although 1 crack was observed in the "intersection between inflow compartments", the crack did not affect soot leakage, and therefore it is considered that: even if such cracks are generated, the performance of the honeycomb filter is not affected. Therefore, the honeycomb filters of examples 1 to 30 can effectively suppress leakage of particulate matter such as soot.

The honeycomb filters of comparative examples 1 to 30 were found to have failed in the overall determination of thermal shock resistance, i.e., "evaluation B" or "evaluation C". In particular, in the "portion separating the inflow cell and the outflow cell", the leakage of soot from the honeycomb filter was confirmed for the honeycomb filter in which the crack was confirmed. In addition, in the "intersection point portion", it is not preferable that the honeycomb filter in which 2 or more continuous cracks are observed has a decreased mechanical strength in structure.

Industrial applicability

The honeycomb filter of the present invention can be used as a filter for trapping particulate matter in exhaust gas.

Claims

1. A honeycomb filter is provided with:

the cell having the plugged portion provided at an end portion on the inflow end surface side and having an opening on the outflow end surface side is defined as an outflow cell,

a cross section of the honeycomb structure portion orthogonal to a direction in which the cells extend includes at least a cell row in which the inflow cells and the outflow cells are alternately arranged with the partition walls interposed therebetween in one direction,

a value obtained by dividing the porosity A by the porosity B, that is, A/B is 0.50 to 0.95,

the porosity B is 25 to 37.9%.

2. The honeycomb filter of claim 1,

the porosity A is 15 to 70%.

3. The honeycomb filter of claim 1,

the sum of the porosity A and the porosity B is 25 to 80% on average.

4. The honeycomb filter of claim 2,

the sum of the porosity A and the porosity B is 25 to 80% on average.

5. The honeycomb filter according to any one of claims 1 to 4,

the inflow cells in a cross section of the honeycomb structure portion orthogonal to a direction in which the cells extend are shaped as a quadrangle, a hexagon, or an octagon.

6. The honeycomb filter of claim 5,

the shape of the outflow cells in a cross section of the honeycomb structure portion orthogonal to the direction in which the cells extend is a quadrangle or a hexagon.

7. The honeycomb filter according to any one of claims 1 to 4,

the open area S1 of 1 of the inflow compartments is greater than the open area S2 of 1 of the outflow compartments.

8. The honeycomb filter according to any one of claims 1 to 4,

the thickness of the partition wall is 100 to 450 μm.